Does anyone have any data on when the earliest SX-42's were made? Seems to me that I saw ad reprints that stated the 1st batch of 100 were built in October, 1946, My chassis is dated October 25, 1946, and going into restoration, had an unmolested circuit consistent with the earliest schematic. But, does anyone have a clear reference point on data? Were any built before October of '46?

I have HA-74051 and HA-77844. I have not seen a date stamp. but I have a square inspector ink stamp on the inside chassis.The first shows a Run # XXX with a Mech Ins OK #63, the second has a Run # 1 with a Mech Ins OK #68. The older SX-42 still had a manilla factory tag tied to the line cord with Final Ins information.Hallicrafters Service Hint # 21 has information on how to decipher the runs and changes:http://pcbunn.cd3.caltech.edu/jjb/Halli ... o%2021.pdf

I dont think I am ever going to solve this. But based on the ads I have seen that Hallicrafters put out in Oct, 46 about the initial run of 100, and the date stamped onto my chassis, I am sticking to it.

You could contact Chuck Dachis? He is a prominent Hallicrafters historian:http://www.hallicraftercollector.com/index.htm I emailed him years back about a pair of Hallicrafters R-649A/URR receivers that I had accrued. He responded with some useful information. The SX-42 likely had pre-production prototypes for evaluation and debugging. Mid-'46 looks like the kick-off date and production ended in early-'48. Chuck may know more. Owners of the DD-1 Skyrider Diversity tried to set up a serial number registry website to find out how many may have been built and how many are left.

I finally got a chance to pull my notes on my SX-42. Mine is serial number HA-68203. On the inside of the chassis is a faded red stamp that states it was run XX and a date of 10/1946. I did not find any exact dates stamped anywhere on the chassis.